Cooling hot gases



March 1K0, 1959A l l J. R.r.c:oBB, JR

' COOLING HOT GASES Filed New. z, 195e INVENTOR. J.R. COBB,JR.

A T T0 RNEVS United States Patent O COOLING Hor GASES Joseph R. Cobb,Jr., Bartlesville, Okla., assignor tol Phillips Petroleum Company,V acorporation of Delaware Application November 2, 1956, Serial No. 620,072

11 Claims. (Cl. 1S3-120) This invention relates to a method andapparatus for preparingy low molecular weight hot cracked gases containing easily' polymerizable materials for subsequent processing underpressure. In one aspect it. relates to a method and apparatus forconducting such. an operation with the production and deposition of aminimum of' polymeric material on the inner surface of' equipmentexposed to the cracked gases. In another aspect it relates to a methodVand apparatus for preparing such gases for processingy at a higherpressure than the pressure at which they were produced, with a minimumof? heat exchange surfaces and. with a minimum of cooling.

It is known that ethylene and other low molecularl weight unsaturatedhydrocarbonsl can 4dvantageously bel produced by high temperaturecrackingbf light hydrocarbons such as ethane, propane,.-buta`r`te`orother'hydr carbons. The present invention is'co'ncerned primarily withthe problem of cooling,l the eiliuenktgases from such' a; crackingprocess and with their l pression in such a manner as to obtain thegasesfat pressure suitable for' subsequent high pressure proczessingVwithout forma-- tion of solid polymeric material orwith the `formationof a minimum of deposited polymeric material on surfaces to which thegases are exposed. The deposited solid polymeric material isbelieved'mainlytheresult of polymerization of diolenic material. suchasbutadiene` and cyclopentadiene in the ethylene containing gasesproduced in the above mentioned hydrocarbon cracking. The amount ofpolymer formed is believed to be a function of the amount of certaintracev hydrocarbons in the Cg-Cm range which are believed to catalyzethis polymerization.

The present invention employs a combination of water quenching and oilquenching steps. Novell heat exchange steps are employed in combinationwith furnace` etlluent quenching. in such a manner as to avoiddeposition of solid polymeric material on the Walls ofl the processingequipment. Mainly the invention comprises av method for preparing hotfeed gases for subsequent high pressure processing comprising the stepsVof cooling; said hot gases by direct heat exchange .with a cool quenchoil, further cooling the cooled gases by direct heat exchange withcooling Water, still further cooling` the further cooled gases by directheat exchange with refrigerated water and compressing the still furthercooled gases to a pressure suitable for said. high pressure processing.

An object of my invention is toprovide apparatus and method for coolingand compressing for subsequent processing cracking still effluent gasesto a lower temperature and a higher pressure than the gases possessedwhen produced. A

Yet another object of my invention is to provide such apparatus andmethod in which polymer formation anddeposition on the inner walls ofthe processing equipment are reduced to a minimum.

Yet another object of my invention is:v to'provide-sucl'l a method andlapparatusl which is, easy andl simpl'efto'- construct and' to operate.

Yet another object of my in ventionv is to providev suchy a method. andapparatus which involves simplied heat; exchangev operations' in such amanner as to avoid use; of tubular heat'V exchangers.

OtherY objectsv andA advantages and features of the in@ vention. willbecome apparent from the following detailed description which, takenwith the attached drawing; formsr a partk ofthisA specification.

In the drawing, the ligure represents, in diagrammatic form, onearrangement of apparatusY parts for carrying; out the processI of myinvention.

When cracking such feed materials as ethane, propane,l butane or otherrelatively low molecular Weight hydrocarbons or mixturesof suchmaterialsfor the production of ethylene, forexample, easilypolymerizable hydrocarbonsv such asacetylene, alkyl substitutedacetylene, butadiene, cyclopentadiene, and heavier olenic andd'iolefinicv hydrocarbons are unavoidably produced. However, evidenceis; available to show that where the C3,v through C12 fraction producedin some quantity in crack'- ing any hydrocarbon has been' removed,polymer production. is retarded* By` use of my invention the amount of'CgA-Cm. hydrocarbons taken to the first stage of compression isl reducedto about one. fourth of that which goes to the compressors using aconventional scheme: In conventional operations iuvolvinghandling of.gases;1 containing ethylene and' such easily;"pol'frrrerizablefmaterials, polymers form on the. inner processing equipment as pipes, heacompressor rotors or cylinders anlthv y conditions equipment has tobel'shut down. and exchange and compressor rotors or cylinders" leanedof Ideposite' polymers. Deposited polymers on inner surface of s119171equipment greatly reduce heat exchange eiiciencies"as`A` is well known.My invention provides a process'and My process was' particularly devisedso asto avoid the' use of conventional heat exchangers.Furthermorefmy-f' process. involves cooling the cracked gases totempera@ 1 tures below ordinary cooling water temperatures.

Referring now to the drawing, a charge stock material which is ethane,propane, butane, and isobut'ane, or rni'x-y turesy ofl two or more ofthese hydrocarbons'. or otherxv low molecular weight hydrocarbonssuitable for use inV producing such amaterial as ethylene, isintroducedv from; a source, not. shown, into my system through a*conduit' I1'. A pump 13 transfers the feed material through a; heatexchanger 15 intol a cracking furnace 17. Heat ex,.-y changer 15 isintended to supply sutlicientheat to vapori'ze. feed stock liquid tomake certain that only Vaporousl feed' enters the cracking furnace.Eliluent from the crackingv furnace is passed through a pipev 1,8,quench water isadded there to from. a pipe 2t), the water beingvaporized by the hot gases'. The furnace ellluent and water vapormixture is passed into aquench tower 2l. Pipe- 1'9" communicates with`the quench tower at anl elevation near its bottom.. The vapors sointroduced into the lower portion of this quench tower how upwardly incountercurrent relation to quench, oil sprayed into the towerAY througha spray ring 42. Battles 39 or other suitable vapor-liquid' contactequipment are provided for promoting eliicient contacting of vapor andoil. Partially cooled vapors are passed through the central portion or'a liquid'.` take-olf tray such as a do-nut tray 43 and rise onupward'through the tower; Water from a pipe 31 is sprayed by: a spray 41 at anelevation appreciably above. the level'of they do-nut tray to providefurther cooling for the ascend-.- ingl vapors... Vapor-liquid'contacting is promoted in thief. section of' the quench tower bybafiies: 3.9. Additional- 'Under sont 3 water which is cooled byrefrigeration to a temperature well below atmospheric is introduced at alevel near the top of the tower throughfa spray ring 37. Additionalbales 39 or other vapor-liquid contact promoting apparatus is alsoprovided in this upper section of the tower. Cooled vapors leave thetower through a pipe 23 and pass to a knock out drum 55 for separationof any liquid formed in the overhead pipe 23 or carried thereinto fromthe tower 21. Liquid separated in knock out drum 55 is removed by way ofpipe 57 for such disposal, depending upon its composition, as desired.Vapors separated in drum 55 are passed on through a pipe 59, arecompressed in a compressor 61 and are passed on into the lower portionof a second cooling tower 63. This tower is also provided with baflies71 or other suitable vapor-liquid contacting apparatus. Cooling water atconventional cooling water temperatures is sprayed through a lspray ring73 to cool the vapors heated by compressor 61 while refrigerated wateris sprayed into the gases in the upper portion of tower 63 through aspray ring 69. Cooled gases leave cooling tower 63 by way of a pipe 65and are compressed in a compressor 81 to such a pressure as desired in asubsequent processing operation. Suchan operation can be an absorptionoperation for extracting the ethylene from the cracked gases. Anycondensate passing through the portion of conduit 65 down stream, asregards direction of ow from compressor 81, is separated in a knock outdrum 83. Separated liquid is removed through a pipe 85 for disposal asdesired, and depending on its composition. Vapors separated in .thisknock out drum are passed to, for example, such a subsequent processingoperation as an absorption operation. Such an 'operation is illustratedas being carried out in an absorber 89, lean absorptionoil beingintroduced thereinto by way of a pipe 93 and rich oil being removedtherefrom through a pipe 95. Gases deleted of the absorbed constituentor constituents are removed from the absorber through a pipe 91.

l Hot quench oil in the bottom of the quench tower- 21 is passedtherefrom through a pipe 25 to the aforementioned heat exchanger 15 toprovide suflicient heat for Vaporizing the feed stock to the operation.The quench oil cooled in this heat exchanger is passed directly througha pipe 27 to spray ring 42 or in some cases it is desirable to coolfurther by atmospheric or other cooling the quench oil prior to itsintroduction through spray ring 42.

The water introduced into quench tower 21 through spray ring 41 isordinary plant cooling Water, the water originating from a source, notshown, and passing by way of a pipe 29 for use in the operationsdescribed herein. From pipe 29 plant cooling water is passed on througha pipe 31 in to the above mentioned spray ring 41. A portion of thewater from pipe 29 is passed through conduit 33 and is refrigerated in aheat exchanger 35 prior to introduction through spray ring 37 into theupper cooling section of quench tower 21. The water introduced throughspray ring 37 and that introduced through spray ring 41 collect on thedo-nut or take-off tray 43 and the collected water and condensed oil areremoved therefrom by way of a pipe 45 and are passed into an oil-waterseparator 47. In this separator oil separates as an upper layer and isremoved through a pipe 49 for such disposal as desired. The water layerfrom the bottom of separator 47 is passed by way of a pipe 51 to aconventional plant cooling tower such as is ordinarily used inindustrial plants.

A portion of the water from the plant cooling towers, not shown, andentering my system by way of pipe 29 is by-passed from quench tower 21and flows through a` pipe 75 for use in the cooling tower 63. A portionof the water from pipe 75 is passed through a pipe 77 and thence throughthe spray ring 73 for cooling the gases in the lower portion of thisvessel. The remainder of the water from pipe 75 is passed through arefrigerated exinto the upper portion of cooling tower 63 through thespray ring 69.

While propylene is a preferred refrigerant for the refrigeratedexchangers 35 "and 79, other refrigerants, such as sulfur dioxide,butano, isobutane, etc., are used under some conditions. Suchrefrigerant systems are well known in the art.

A vent pipe 53 is provided for the oil-water separator 47 in casepressure relief is necessary.

Water sprayed through spray rings 69 and 73 and condensed oil flow tothe bottom of cooling tower 63 and are removed therefrom by way of apipe 67 and is combined with the water from pipe 45 for passage into theoil-water separator 47.

In describing briefly the above operation it will be realized that suchequipment as valves, ow controllers, ratio flow controllers, meters,pressure indicating and recording equipment and the like are provided atproper process points for maintaining proper control of the process.Such equipment, their installation and use, are well understood by thoseskilled in the processing art.

As a specific example of the operation of the process of my invention, amixture comprising normal butane and isobutane is introduced intofurnace .17 through conduit 11. These two gases are supplied in theratio of 972 mols of normal butane to 28 mols of isobutane. From a pipe16 is introduced into this feed mixture 249 mols of water per 1,000 molsof the feed mixture in the form of steam. The hydrocarbon and steammixture is heated rapidly in furnace 17 to a furnace outlettemperature-`of about 1,500 F. Inlet pressure to the furnace is about 85 pounds persquare inch yabsolute (p. s. i. a.). .An appreciable pressurevdropoccurs on passing through the furnace and the gases issue therefrom intopipe 18 at a'pressure of about 20 p. s. i. a. at the above mentionedabout 1,500 F. 1,240 mols of liquidI water at approximately 100 F. areintroduced into pipe 18 from pipe 20 to quench the furnace eluent toabout 900 F. to prevent or at least retard further cracking or undesiredside reactions.

Quench oil is supplied to quench tower 21 at about 140 F. and at a rateof about 1,920 mols per 1,000 mols of feed gas. The quench oil cools thehot gases from the water quench temperature of about 900 F. to about 180F. By this heat exchange the quench oil is heated to about 375 F. andthe quench oil at this temperature is used in exchanger 15 for makingcertain that the feed to the operation is in the gaseous condition. Asmentioned above, additional heat exchange can be employed to cool thequench oil from exchanger 15, if desired, prior to reintroduction intotower 21 to make certain that the oil introduced thereinto has atemperature of about 140 F.

The oil quenched gases pass through the do-nut tray 43 and rise upwardand are cooled by plant cooling water from spray ring 41 to about 116 F.The refrigerated water, cooled by propylene refrigeration in exchanger35, is sprayed into the top of this tower at a temperature of about 52F., the gases being cooled thereby to a temperature of about 58 F. Therefrigerated water from spray ring 37 and the plant cooling water fromspray ring 41 reach the do-nut tray at a temperature of about 150 F. Therefrigerated water from spray ring 37 changer 79 and on through a pipe80 for introduction 75 reaches a temperature of about F. by the time itreaches the top of spray ring 41. The cooled gases leave the top of thisquench tower through pipe 23 at a temperature of about 58 F. and at apressure of about 18 p. s. i. a. It is noted that the cracked gases andsteam entering quench tower 21 have a pressure of about 20 p. s. i. a.and experience a pressure drop of only about 2 p. s. i. a. on passing'through the length of this quench tower. That point is one of theimportant advantages of my invention, that is, the pressure dropexperienced by the relatively low pressure gases is relatively small oupassing through this heat exchange operation. It is realized that thesame flow of gases passing through conventional tube heat exchangers forindirect heat exchange would? experience a much greater pressure drop bythe time they were cooled to the same temperature at Whichthe gasesleave quench tower 21. Furthermore, at these relatively low pressureslarge heat exchange surfaces are required. As a result of the relativelylow pressure drop in quench tower 21, the compression load ofasubsequent compressor is greatly reduced for compressing the cooledgases to a subsequent processing pressure. Compressor 61 compresses the18 p. s. i. a. gases to a pressure of about 67 p. s. i. a. and the gasesexperience an increase in temperature from about 58 F. to. about 250 F.by this compression. At this orlower temperatures polymer formation isquite small.

The oil condensed by the refrigerated water in the upper portion of.vessel 21 contains an appreciable amount of the hereinbefore mentionedC8 to C12 hydrocarbon fracare` thoseV for` vaporizing the feedstock(i151) andforzthel propylene refrigeration (35, 79) of the water.Thezwaterr issuing from. the. propylenearefrigerated exchangers. and:`79 has atemperaturei ofk about 52 F. and the, propyliene issuingtherefrom hasv a: temperature. ofk about 42r F. I nd that while otherrefrigerants can beY successfullyused ink this: service, propylene. iswell suited to the op-V eration. andr is` a preferred refrigerant. Theparticular propylene.- refrigeration. systememployed can be oneconstructed along conventional lines,v the only specific. requirementbeing that. itbe adapted to cool the. water in the refrigeratedexchangers to a temperaturev of about 52 F.

Summing up'the. operation ofthe above example is the: following; table.which givesl product compositions; with` respect to hydrocarbons and.water contents a-t various processing points. The compositions aregiven in terms: of,` pound mol-sv per hour.

Processing Point (19) (27) f' (25)l (23) (45) (65) (67) Feed to QuenchQuenchl Over- Water lCooled Mols per Hour Quench Oil Oil head Out Over-Bottoms Tower In Out 15D,o F f Head (31) Cooling tower water in at 110F., 31,200 mols per hour.

(33) Refrigerated water in at 52 (77) Cooling tower water-inv at 1109 FE., 3,620mols per hour.

l., 580 mois. per hour.

(79) Reirlgerated Water in at 52' F., 639 mols per hour.

tion. As previously mentioned, my process removes more of these C8 toC12 hydrocarbons than do conventional processes. By removing a greaterproportionV of these hydrocarbons a somewhat higher compressor outlettemperature of the ethylene containing stream (about 250 R), can betolerated without excessive fouling of process equipment over thattolerated by prior art processes in which compressor outlet temperaturesare held to about 200 F. to avoid excessiveY polymer deposition.

In order to compress further these gases I provide the additionalcooling tower 63 in which an additional quantity of plant cooling wateris sprayed through spray ring 73 and additional refrigerated water issprayed through spray ring 69 to cool again the gases to a temperatureof about 58 F. The plant water through spray ring 73 and therefrigerated water through spray ring 69 have the same correspondingtemperatures as those utilized in quench tower 21. The 52 F. water fromspray ring 69 increases in temperature to about 102 F. by the time itreaches spray ring 73. Plant water at 110 F. combines with this 102 F.Water and they reach a temperature of about 140 F. in the bottom of thiscooling tower. The gasesv are cooled in the lower portion of this towerto a temperature of about 116 F. by the time they pass the spray ring 73into the upper portion of the tower. Cooled gases leave tower 63 at atemperature of about 58 F. and at a pressure of about 65 p. s. i. a. andupon further cornpression in compressor Si the gases reach thesubsequent processing step illustrated by absorber 89 at about 100 F.,i. e., at ambient temperature, and at a pressure of about 170 p. s. i.a. By ambient temperature, ,I meanf atmospheric temperature. Y

It will be noted that in the illustration givenl hereinabove I have notemployed a tube-containing heat ex-y changer for any cooling step of thecracked gases. The only tube containing heat exchangers whichv I`haveused,

In the abover illustrated process a smaller than converttional pressuredrop was experienced on passing through quench tower 21 and coolingtower 63 than through conventional tube containing heat exchangers, andtherefore lessl horse power isrequired for compressing the final cooledgases to the same' pressure of about 170 p. s. i. a. at F. When usingconventional tube containing exchangers, the horse power required perhourk per 1,000 pound molsv of feed: gas tov the. system for thiscompression is 4,390 in comparison to only 3,690. horsepower required inthe process. abovey described, including refrigeration requirementsz.This. diterencez in power require mentA is appreciable when consideredon a 1,000 pound. mol feed gas-basis'.

From the above detailed description it'. is. seen that my inventioncauses less pressure drop of gases being cooled. than when employingtubey containing heat exchangers, which, as mentioned, resultsin asaving in compression requirements. Furthermore, by being able to avoidentirely the use of tube containing eat exchangers there is no foulingof heat exchange surfaces because of deposited polymer, with theresult'that stand-by exchangers need not be provided when the exchangerswhich havei been on stream' need. to be tty-passed for cleaningpurposes. As isl well known, such cleaning of' heat exchangers is acostly operation. v

Furthermore, by use of' an oil quench and direct water quench(refrigerated.) cooling steps, polymer forming agents are removed` fromthe cracked gas streamv to aconsiderable. extent. by solution in the oiland such removal' further assists in elimination of deposited polymer onthe processing equipment. Also, the smaller pressure dropk through bydirect quenchand heat exchangers requires less compression and,therefore, less heating, of the gasesl and less heatngpby compressionalso assists in reducingpolymer formation and deposition on theprocessing equipment.

While I have disclosed compressors 61 and 81 as being single stagecompressors, they can, if desired, be multistage compressors. In likemanner, I have disclosed two cooling vessels 21 and 63, but it will beobvious that depending on the service, more than two cooling stages areused where required, each involving use of plant cooling water andrefrigerated water, the flrst stage obviously employing quench oil asdisclosed in vessel 21.

The quench oil employed is substantially any heavy oil, parainic oraromatic, which will flow and can be sprayed at the lowest temperaturesinvolved. A preferred oil is a heavy aromatic oil which is produced inthe cracking operation and permitted to accumulate in the process. Oilfor starting the operation and make up oil, if required, is introducedinto the system through a pipe 26. However, if an excess of oil isproduced Vin the operation over that required for quenching and heatexchange purposes, this excess oil is removed through pipe 26. Such anoil as is suitable for quench purposes in my operation has the followingcharacteristics:

Specific gravity at 60/60 F.=l.0655

Kinematic viscosity at 100 F.=14.38 centistokes Kinematic viscosity at210 F.=2.86 centistokes Bureau of Mines correlation index=133 ASTMdistillation, corrected to 760 mm. Hg

In the operation of my process utilizing such a feed stock as hereindisclosed there is little undesirable polymer formation in compressorsand piping as long as temperatures of the ethylene containing gases aremaintained at about 250 F. and below. Itis believed that the quench oilabsorbs out a portion of the easily polymerizable material, but thatmaterial remaining in the gases undergoing treatment does not polymerizeand deposit on equipment to any great extent as long as the temperatureis maintained at about 250 F. and below.

While certain embodiments of the invention have been described forillustrative purposes, the invention obviously is not limited thereto.

It .has been found that when the temperature of the gases leaving thequench tower 21 through line 23 is below about 60 F. that compressor 61will run much longer without polymer deposit therein than if thetemperature is above about 60 F., so that as to this specic aspect ofabout 60 F. in line 23 this temperature is in fact critical to completepolymer removal by the time the iluid undergoing treatment leaves vessel21.

I claim:

1. A process for preparing low pressure, high temperature cracked gasescontaining ethylene and easily polymerizable hydrocarbons for subsequentprocessing at a pressure higher than said low pressure and at ambienttemperature comprising the steps of quenching said high temperaturecracked gases by direct heat exchange with a cool quench oil, coolingthe quenched gases by direct heat exchange with plant cooling water,further cooling the cooled gases by direct heat exchange withrefrigerated water, compressing the further cooled gases to such apressure that the compressed gases issue from said compress or at atemperature of about 250 F., cooling the compressed gases by direct heatexchange with plant cooling water, still furthercooling these lattercooled gases by direct heat exchange with refrigerated water, andcompressing the still further cooled gases to such a pressure higherthan the aforesaid low pressure that compressed gases issuing from thislatter compression step issue therefrom at substantially ambienttemperature.

2. In the process of claim 1 wherein said refrigerated Water possesses atemperature of about 52 F.

3. In the process of claim l wherein said plant cooling water possessesa temperature of about 100 F., and said refrigerated water possesses atemperature of about 52 F., and said ambient temperature is about 100 F.

4. ln the process of claim l wherein the first mentioned compressionstep compresses said gases to a pressure of about 67 p. s. i. a. and thesecond mentioned compression step compresses the still further cooledgases to a pressure of about 170 p. s. i. a.

5. A method comprising quenching hot cracked hydrocarbon gases by directheat exchange with a cool quench oil in a first quench zone, withdrawingquenched gases from said first quench zone and cooling the withdrawngases by direct heat exchange with plant cooling water in a firstcooling zone, passing cooled gases from said first cooling zone into asecond cooling zone and therein further cooling the cooled gases bydirect heat exchange with refrigerated water, withdrawing further cooledgases from said second cooling zone, combining the refrigerated waterfrom said second cooling zone with the plant cooling water in said firstcooling zone and withdrawing the combined stream of Water from saidfirst cooling zone, compressing the withdrawn further cooled gases in acompression zone to such a pressure that the compressed gases issuingfrom the compression zone issue therefrom at a temperature below whicheasily polymerizable materials in said cracked gases form solidpolymeric material, cooling the compressed gases in a third cooling zoneby direct heat exchange with plant cooling water, further cooling theselatter cooled gases in a fourth cooling zone by direct heat exchangewith refrigerated water, combining the water from the fourth coolingzone with the water in the third cooling zone and withdrawing thiscombined water from said third zone, withdrawing the cooled gases fromsaid fourth cooling zone, compressing these latter cooled gases in asecond compression zone to a pressure that the compressed gases issuetherefrom at ambient temperature, said compressed gases at ambienttemperature being suitable for subsequent processing.

6. In the process of claim 5 wherein the temperature of saidrefrigerated water is about 52 F., said ambient temperature is about F.and the pressure of the gases issuing from said second compression zoneis about p. s. 1. a.

7. A method for preparing high temperature cracked hydrocarbon gasescontaining easily polymerizable constituents for subsequent highpressure processing comprising cooling the high temperature crackedgases by quenching with water to a temperature of about 900 F.,quenching the water quenched gases by direct heat exchange with a coolquench oil, cooling the oil quenched gases by direct heat exchange withplant cooling water, and further cooling the cooled gases by direct heatexchange with refrigerated water, and subsequently compressing thefurther cooled gases to a pressure suitable for subsequent processingwhereby the temperature of the compressed gases is maintained at a valuebelow that at which solid polymers are formed and deposited on the wallsof the processing equipment.

8. A process for preparing low pressure, high temperature cracked gasescontaining ethylene and easily polymerizable hydrocarbons for subsequentprocessing at a pressure higher than said low pressure and at atemperature below said high temperature comprising the steps ofintroducing a cool quench oil into the upper portion of a hightemperature quench section of a heat exchange zone, introducing said lowpressure, high ternperature gases into the lower portion of said hightemperature'quench section, introducing plant cooling water into theupper portion of a first water cooling section of said zone, the lowerportion of said first water cooling section being above and incommunication with the upper portion of said quench section, introducingrefrigerated water into the upper portion of a second water coolingsection of said zone, the lower portion of said second water coolingsection being above and in communication with the upper portion of saidiirst water cooling section, counter-currently contacting said coolquench oil and the introduced high temperature gases in said quenchsection whereby said introduced gases are quenched, passing the quenchedgases from the upper portion of said quench section into the lowerportion of said first water cooling section and therein countercurrentlycontacting said quenched gases with said plant cooling water wherebysaid quenched gases are cooled, passing the cooled gases from the upperportion of said first water cooling section into the lower portion ofsaid second water cooling section and therein countercurrentlycontacting same with the introduced refrigerated water whereby the gasesare further cooled, mixing the countercurrently contacted refrigeratedwater with the introduced plant cooling water prior to thecountercurrent contacting of the quenched gases with said plant coolingwater, withdrawing the further cooled gases from the upper portion ofsaid second water cooling section and compressing same to a pressurehigher than the aforesaid low pressure, withdrawing the compressed gasesfrom the cornpressing step at a temperature below which appreciablepolymerization of said polymerizable material occurs, withdrawingcountercurrently contacted quench oil and the mixed plant cooling waterand refrigerated water respectively from the quench section and the rstwater cooling section of said heat exchange zone, introducing thecompressed gases into the lower portion of a second heat exchange zone,introducing plant cooling water into said second zone at a level aboutmidway from top to bottom thereof, introducing refrigerated water intosaid second zone at about the top thereof, the portion of the secondzone above the level of introduction of said plant cooling water beingthe upper portion and the portion below said level being the lowerportion thereof, countercurrently contacting the introduced compressedgases with a mixture of the last mentioned plant cooling water and thelast mentioned refrigerated water as subsequently produced in said lowerportion of this second zone, passing these latter countercurrentlycontacted gases into the upper portion of said second zone and thereincountercurrently contacting same with the refrigerated water introducedinto said second zone, passing this latter countercurrently contactedrefrigerated water into the lower portion of said second zone and mixingsame with said plant water introduced thereinto as said mixture ofcooling Water and refrigerated water as subsequently produced,withdrawing the nally countercurrently contacted gases from the upperportion of said second zone, compressing these latter withdrawn gases toa pressure higher than the aforementioned compression step, withdrawingthese nally compressed gases from this latter compression step at anambient temperature and withdrawing the countercurrently contacted plantcooling water and refrigerated water from the lower portion of saidsecond zone.

9. A method for preparing high temperature cracked hydrocarbon gasescontaining easily polymerizable constituents for subsequent highpressure processing comprising cooling the high temperature crackedgases by quenching with water to a temperature of about 900 F.,quenching the water quenched gases by direct heat exchange with a coolquench oil, cooling the oil quenched gases by direct heat exchange withcooling water, and further cooling the cooled gases by direct heatexchange with further cooled Water, and subsequently compressing thefurther cooled gases to a pressure suitable for subsequent processingwhereby the temperature of the compressed gases is maintained at a valuebelow that at which solid polymers are formed and deposited on the wallsof the processing equipment.

10. A method for preparing high temperature cracked hydrocarbon gasescontaining easily polymerizable constituents for subsequent highpressure processing comprising cooling the high temperature crackedgases by a water quench to a temperature at least to retard undesiredside reactions, quenching these water quenched gases by direct heatexchange with a cool quench oil, cooling the oil quenched gases bydirect heat exchange with plant cooling water, and further cooling thelatter water cooled gases by direct heat exchange with refrigeratedwater, and subsequently compressing the further cooled gases to apressure suitable for subsequent processing whereby the temperature ofthe compressed gases is maintained at a value below that at which solidpolymers are formed and deposited on the walls of the processingequipment.

11. A process for preparing low pressure, high temperature, crackedgases containing ethylene and easily polymerizable hydrocarbons forsubsequent processing at a pressure higher than said low pressure and atambient temperature comprising cooling said high temperature crackedgases by a water quench to a temperature of about 900 F., quenching thewater quenched gases by direct heat exchange with a cool quench oil,cooling the oil quenched gases by direct heat exchange with plantcooling water, further cooling the latter cooled gases by direct heatexchange with refrigerated water, compressing the finally cooled gasesto such a pressure that the compressed gases issue from the compressorat a temperature of about 250 F., cooling the compressed gases by directheat exchange with plant cooling water, still further cooling the lattercooled gases by direct heat exchange with refrigerated water, andcompressing the still further cooled gases to such a pressure higherthan the aforesaid low pressure that compressed gases issuing from thislatter compression step issue therefrom at substantially ambienttemperature.

References Cited in the tile of this patent UNITED STATES PATENTS

1. A PROCESS FOR PREPARING LOW PRESSURE HIGH TEMPERATURE CRACKED GASESCONTAINING ETHYLENE AND EASILY POLYMERIZABLE HYDROCARBONS FOR SUBSEQUENTPROCESSING AT A PRESSURE HIGHER THAN SAID LOW PRESSURE AND AT AMBIENTTEMPERATURE COMPRISING THE STEPS OF QUENCHING SAID HIGH TEMPERATURECRACKED GASES BY DIRECT HEAT EXCHANGE WITH A COOL QUENCH OIL, COOLINGTHE QUENCHED GASES BY DIRECT HEAT EXCHANGE WITH PLANT COOLING WATER,FUTHER COOLING THE COOLED GASES BY DIRECTED HEAT EXCHANGE WITHREFRIGERATED WATER, COMPRESSING THE FURTHER COOLED GASES TO SUCHPRESSURE THAT THE COMPRESSED GASES ISSUE FROM SAID COMPRESSOR AT ATEMPERATURE OF ABOUT 250* F., COOLING THE COM-